Time-interleaved analog-to-digital converters (ADCs) can include a digital background calibration of interleaved offset, gain, and time-skew. There are many different implementations of each type of calibration. Some techniques utilize foreground calibration, while other techniques utilize background calibration. Some techniques calibration in the digital domain, while other techniques calibration in the analog domain.
In particular, a time-interleaved ADC can include an offset calibration block (OCB) configured to measure the average of the ADC output signal and remove offset. There is a limitation for signals at multiples of the channel sampling frequency. When the ADC samples a signal with an input frequency at multiples of its sampling frequency, the signal is aliased to DC and hence ends up being removed by the OCB (i.e., the OCBs remove the sampled signal completely). It is desirable to provide a technique for offset calibration that avoids this limitation.